Reactions Online lecture

Metathesis Double Replacement Reactions

Basics  Exchange of ________  Never a redox – no change in oxidation #  Must have a driving force in order to go to completion 1) 2) 3)

About those Gases H 2 S any S -2 + acid  H 2 S + salt CO 2 any CO acid  CO 2 * + H 2 O* + salt SO 2 any SO acid  SO 2 * +H 2 0* + salt NH 3 any NH 4 +1 salt + strong base  NH 3 *+ HOH* + salt MEMORIZE (*ask me)

These ARE NOT Molecular Species Strong Acids – always ionize HClO 4, HClO 3, HCl, HBr, HI, HNO 3, H 2 SO 4 Strong Bases – always dissociate Group 1 and Ba, Sr, Ca NH 4 OH doesn’t exist it is always NH 3 + HOH Soluble Salts – always dissociate into ions

These ARE Molecular Species Weak Acids, Weak Bases and WATER THEY DO NOT BREAK APART EVER!!!! Neutralization Reaction – produces H 2 O Strong Acid + Strong Base  HOH + Salt

Forming a Precipitate  Solid ammonium carbonate is added to a saturated solution of barium hydroxide.  Solutions of cobalt (II) nitrate and sodium hydroxide are mixed.  A solution of copper (II) chloride is added a to a solution of sodium sulfide.

Forming a gas or water/molecular species  Ammonium chloride crystals are added to a solution of sodium hydroxide  Sodium acetate solution is mixed with excess hydrochloric acid.  Hydrobromic acid is added to a solution of sodium sulfite.

Single Replacement Its always redox!!!

What is redox?  Oxidation States- learn the rules.  Oxidation is the ______________. Oxidation number is more positive.  Reduction is the ______________. Oxidation number is more negative.  These occur together- REDOX – a __________ of electrons. ____ the lion goes ____

The Rules: (pg 171)  Uncombined Elements are always zero. This includes the diatomics.  Ionic compounds – charge is oxidation number  Fluorine is -1 in compounds.  Oxygen is -2 in compounds, except in peroxides its -1.  Hydrogen is +1. Assign oxidation states to all the atoms in the following. a. CO 2 b. SF 6 c. NO 3 -

What you need to be able to do with redox!  The exam generally gives a complete, but unbalanced equation.  You must balance the elements as well as the charges.  Be able to recognize what is oxidized and what is reduced

Balancing Oxidation-Reduction Reactions 1. Determine the oxidation states of all parts of the reactants and products. 2. Show how the oxidation and reduction occur. 3. Use coefficients to equalize the electrons gained or lost. 4. Balance the rest by inspection. 5. Check. 6. Net charge of reactants = net charge of products

Lets try: PbO(s) + NH 3 (g)  N 2 (g) + H 2 O(l) + Pb(s)

Lets try: Cu (s) + Ag + (aq)  Ag (s) + Cu +2 (aq)

Single Replacement: exchange of either the metal or nonmetal  Element by itself on the reactant side will tell you if it’s a metal or nonmetal exchange  All reactions take place  These are always redox, meaning a transfer of electrons has occurred.  LEO the lion goes GER  For example  Metal - Li (s) + CaCl 2(aq)  LiCl (aq) + Ca (s) molecular Li (s) + Ca +2 (aq)  Li +1 (aq) + Ca (s) net ionic

Couple of things to remember  Write the net ionic  The lone metal or lone nonmetal on the reactant side will always be (s) for the metal or (s) or (l) for the nonmetal and has no charge. It then becomes (aq) and with a charge as a product.  The metal or nonmetal on the reactant side that will be replaced is always (aq) and has a charge. It then becomes a (l) or (s) as a product and has no charge. Li (s) + CaCl 2(aq)  LiCl (aq) + Ca (s) molecular Li (s) + Ca +2 (aq)  Li +1 (aq) + Ca (s) net ionic  WATCH YOUR DIATOMICS!!!!!!!!!!!!!!!!!!!  Charge on reactant side = Charge on product side

Let’s try it Liquid bromine is added to a container of sodium iodide solution. An aluminum strip is immersed in a solution of silver nitrate.

Synthesis and Decomposition

These reactions are the opposite of each other.  Synthesis, Composition or Combination – two elements or two compounds are put together to form one product.  Decomposition – one compound breaks down into two elements, two compounds or a compound and an element  Basically this is a lot of memorization, so I would learn the synthesis and then realize the decomposition is the opposite.  I would only focus on the really common synthesis and decomposition reactions.  Keep in mind decomposition will generally mention the application of heat or electricity in order to get the reaction to occur.

Here are the memorize or die synthesis and decomposition!  Metal + nonmetal  ionic compound  Metallic oxide (Na 2 O) + HOH  metallic hydroxide (NaOH)  Nonmetallic oxide (CO 2 ) + HOH  acid  Metallic oxide (Na 2 O) + CO 2  metallic carbonate (Na 2 CO 3 )  Metallic oxide (Na 2 O) + SO 3  metallic sulfate (Na 2 SO 4 )  (NH 4 ) 2 CO 3  NH 3 + H 2 O + CO 2  2H 2 O 2  2H 2 O + O 2

Remember to write net ionics.  A sample of calcium carbonate is heated  Sulfur dioxide gas is bubbled through water.  A pea-sized piece of sodium is added to a container of iodine vapor.  Liquid hydrogen peroxide is warmed.

Please go to the wiki page for practice worksheets.